The Oversized Battery Spiral

A fixed-battery commercial EV is not sized for the trip it makes. It is sized for the worst trip it will ever make, on the worst day of its battery's life. Everything beyond that is weight it carries but rarely uses.

This is the oversizing problem. It is visible in the published specifications of almost every commercial EV sold in India today, and it has a measurable cost in capital, weight, and battery life.

What Indian Commercial EVs Actually Carry

Battery weights are estimated from capacity at a pack-level energy density of approximately 120 Wh/kg, a standard LFP figure, and marked as estimates.

Light Commercial Vehicles

Vehicle	Battery (kWh)	Range (km)	Est. weight (kg)	Full charge
Tata Ace EV	21.3	154	~178	~105 min fast [1]
Tata Ace EV 1000	21.3	161	~178	~105 min fast [2]
Mahindra Zeo	21.3	160	~178	overnight AC [3]
Jupiter JEM Tez	30.24	190+	~252	4 hr AC / 1 hr fast [4]
Eka K1.5	32	180	~267	4–5 hr [5]

Buses

Vehicle	Battery (kWh)	Range (km)	Est. weight (kg)	Full charge
JBM ECO-LIFE (12m)	261	150–200	~2,175	overnight + opportunity [6]
Tata Starbus EV (12m)	300–400	150+	~2,500–3,300	2–3 hr fast [7]
Olectra K9	250+	250–300	~2,080+	3–4 hr [8]
Eicher Skyline Pro E (9m)	204	up to 300	~1,700	2–3 hr [9]
BMTC Tata low-floor (12m)	200	200	~1,667	overnight [10]

Trucks

Vehicle	Battery (kWh)	Range (km)	Est. weight (kg)	Full charge
Tata Ultra T.7 EV (discontinued)	62.5	100	~520	2 hr DC fast [11]
Ashok Leyland Boss 19T EV	201.5	194	~1,680	fast charge [12]
Tata Prima E.28K	250–453	150–220	~2,080–3,775	~55 min DC 0–80% [13]
IPLTech Rhino 5536e	258	185	~2,150	90 min [14]

The Pattern Gets Worse as Vehicles Get Bigger

In the LCV table, the cluster around 21 kWh shows the oversizing problem is contained at small scale. The delta between vehicles is modest, the weight penalty is small, and the cost of overspecification is bearable.

In the bus and truck tables, the spread widens. Bus batteries range from 200 to 400+ kWh for comparable route coverage. Truck batteries swing from 62 kWh to 450 kWh. Three things compound as vehicles get larger.

First, vehicle efficiency falls as more battery weight is added, because the vehicle has to move the extra battery, requiring still more battery to maintain range. This is the dead-weight spiral.

Second, depth of discharge buffers grow in absolute terms. A 10% DoD buffer on a 21 kWh LCV is about 2 kWh of unused capacity. The same 10% buffer on a 400 kWh bus is 40 kWh, paid for and carried on every trip.

Third, the cost of overspecification grows non-linearly. An extra 50 kWh on an LCV is a marginal pricing decision. An extra 100 kWh on a bus or truck is several lakhs of capital, kept on the vehicle for years.

Why Manufacturers Oversize

The case for larger batteries, made across the industry, is that they reduce operating currents, lower thermal load on the cells, and extend battery life by spreading charge and discharge across more capacity.

Inside the conventional fast-charging architecture, this reasoning is correct. The battery has to absorb whatever the charger delivers. Bigger packs spread the thermal load. Lower C-rates extend life. Longer range reduces charging frequency. Operators accept the weight, the capital, and the dead-asset penalty because the alternative, a small battery with frequent charging, makes the vehicle unviable.

The trap is visible at both ends of the market. The Tata Ultra T.7 EV, India's first electric intermediate commercial vehicle, was discontinued. Industry sentiment widely attributes its short commercial life to the same combination of constraints: a 100 km range and a 2-hour fast charge on a 62.5 kWh battery made the total cost of ownership and operational utility too weak to scale in urban logistics.

The Mitsubishi Fuso eCanter illustrates this trap globally. Launched in 2017 as Japan's first series-produced electric light-duty truck, it carries an 82 kWh battery, of which 66 kWh is usable. The remaining 16 kWh, roughly 20%, is a DoD buffer the operator pays for but never uses [15]. DC fast charging takes one hour for 80% of capacity [16]. Adoption has been slow. By 2018, two years after launch, 150 units had been delivered globally [17]. By 2021, 300 units. By 2022, around 450. By 2023, only 550+ vehicles in customer hands worldwide [18]. The OEM's response in the next-generation 2022 model was to expand the lineup to 42 chassis variations with "options for driving range," extending battery configurations upward [19]. The bitter pill of oversizing is what the market actually buys.

The premise underneath all of this is that the only way to refill energy is to plug a vehicle into a charger. Inside that premise, oversizing is unavoidable.

The Route Reality

Here is where the oversizing becomes visible at the operational level.

A Bengaluru city bus under current lease agreements is contracted to run approximately 200–225 km per day [10][20]. It does not run that distance in one stretch. It runs in trips, returning to or passing its depot between them. The fleet collectively operates around 61,000 trips across 1.19 million km daily, an average of roughly 19 km per trip [21]. Even allowing for longer routes, a typical intracity bus completes individual trips of around 40 km before it is back at a point where a swap could occur.

A bus carrying a 200 kWh battery, capable of 200 km of range, uses roughly 40 km of that range, about 20%, on a typical trip. It carries the other 80% as insurance. That insurance has a weight, around 1,600 kg, and a cost, ₹20–24 lakh ($21k–$25k) at LFP pack prices. It is carried on every trip and used on almost none of them.

What Swapping Changes

A swappable bus for intracity duty carries 60 kWh, sized for the next inter-swap interval rather than the full day. Our architecture scales upward to 180 kWh for intercity routes, but the intracity case is the cleanest comparison.

Including 14% station energy inventory, the total system energy requirement is 60 × 1.14 ≈ 68 kWh per bus equivalent.

The smallest fixed-battery intracity bus in commercial service today carries 200 kWh. Against that floor, the swappable system at 68 kWh is 66% less battery per bus, even after accounting for the station-side inventory we hold to keep swaps instant. The battery charges slowly, in a controlled environment, away from the heat of a vehicle in traffic, so it ages far slower than a fast-charged fixed pack [22][23].

Swapping breaks the premise that refilling energy requires plugging into a charger. With that premise gone, the case for oversizing disappears with it.

The Close

The oversized battery is not a flaw in fixed-battery EVs. It is the logical result of asking one battery to be two things at once: the vehicle's energy source for its hardest day, and its insurance against its own decline.

Swapping separates those functions. The vehicle carries the energy it needs for the next 40 km. The infrastructure owns and manages the asset. The throughput-capex ratio explains why that separation also makes the network cheaper to build. The battery stops being a liability the operator carries, and becomes an asset someone equipped to manage it actually manages.

Sources & Citations

[1] Tata Motors — Electric Truck Battery and Performance Guide, September 2025. Tata Ace EV: 21.3 kWh LFP, 154–161 km certified range. https://trucks.tatamotors.com/blogs/tata-electric-truck-battery-and-performance-guide

[2] CMV360 — Tata Ace EV 1000: 21.3 kWh, 161 km range, 1000 kg payload. https://www.cmv360.com/trucks/tata/ace-ev-1000

[3] CarDekho Trucks — Mahindra Zeo: 21.3 kWh liquid-cooled battery, 160 km real-world range. https://trucks.cardekho.com/en/news/detail/mahindra-zeo-launched-explore-price-features-on-board-range-2478.html

[4] Jupiter Electric Mobility — Manufacturer specifications, March 2025. JEM Tez: 30.24 kWh LFP, 190+ km real-world range, 4 hr AC charging at 7.5 kW; CCS2 DC fast charging delivers 100 km range in 1 hour. https://www.mobilityoutlook.com/features/from-railways-to-roadways-jupiter-electric-mobilitys-strategic-ev-expansion/

[5] Manufacturer specifications — Eka K1.5: 32 kWh, 180 km range, 4–5 hr charge.

[6] YoCharge — Top 10 Best Electric Buses in India, February 2026. JBM ECO-LIFE: 261 kWh, 181 kW motor, 150–200 km. https://yocharge.com/blog/top-10-best-electric-buses-in-india/

[7] Tata Motors Starbus EV brochure (12m variant), distributed via Mithila Motors. 300–400 kWh battery configuration. Specification range pending further verification from Tata Motors official source. https://mithilamotors.com/wp-content/uploads/products/bus-van/EVBus-Starbus-9-12.pdf

[8] Manufacturer and industry specifications — Olectra K9: LFP battery 250+ kWh, 250–300 km range.

[9] 91Trucks — Eicher Skyline Pro E 9m: up to 204 kWh, up to 300 km range. https://www.91trucks.com/buses/electric

[10] Deccan Herald — BMTC to Induct 100 Low-Floor E-Buses, 2024. Tata 12m low-floor: 200 km per charge, charged overnight at depot. Lease stipulates 225 km/day utilisation. https://www.deccanherald.com/india/karnataka/bengaluru/bmtc-to-induct-100-low-floor-e-buses-on-tuesday-2824203

[11] TractorJunction Trucks — Tata Ultra T.7 Electric: 62.5 kWh, 100 km range, 2 hr DC fast charging. https://trucks.tractorjunction.com/en/tata-truck/ultra-t7-electric

[12] Ashok Leyland (manufacturer's own website) — Boss 19T Electric: 201.5 kWh battery, 194 km range, 150 kW power, 18.5T GVW. https://www.ashokleyland.com/in/alternatefuels/ev/boss-19t-electric

[13] CMV360 and Tata Motors — Tata Prima E.28K tipper: 250–453 kWh across configurations, 150–220 km range, DC fast charge ~55 min (0–80%). https://www.cmv360.com/trucks/tata/prima-e28k

[14] YoCharge — IPLTech Rhino 5536e: 258 kWh, 185 km range, 90 min charge. https://yocharge.com/blog/top-electric-trucks-in-india-2025/

[15] EVMagz — Mitsubishi Fuso eCanter Specifications. Total battery 82 kWh, of which 66 kWh usable; ~20% held as depth of discharge buffer; 100 km range. https://evmagz.com/mitsubishi-fuso-ecanter-electric-truck-specifications-battery-and-range/

[16] Wikipedia — Fuso eCanter: DC fast charging delivers 80% capacity in 1 hour via CCS-Type-2 charger. https://en.wikipedia.org/wiki/Fuso_Ecanter

[17] InsideEVs — Fuso Delivered 150 eCanter Distribution Trucks Globally, March 2020. https://insideevs.com/news/402275/fuso-delivered-150-ecanter-trucks/

[18] Daimler Truck — Press release on Next Generation eCanter, September 2022. ~450 vehicles delivered to customers across Japan, Europe, North America, Australia, and New Zealand over five years. https://www.daimlertruck.com/en/newsroom/pressrelease/world-premiere-daimler-truck-subsidiary-fuso-unveils-the-next-generation-ecanter-52027336

[19] Electrive — Fuso Commences Production of Next-Gen eCanter in Europe, May 2023. Next generation expanded from single 7.49-tonne configuration to 42 variations with "options for driving range." https://www.electrive.com/2023/05/22/fuso-commences-production-of-next-gen-ecanter-in-europe/

[20] Deccan Herald — BMTC midi-bus tender requirement: minimum 180 km/day operation for 350 days/year. https://www.deccanherald.com/amp/story/india/karnataka/bengaluru/bmtc-likely-to-run-full-length-e-buses-on-metro-feeder-routes-3317269

[21] Sustainable Bus — Bangalore Buses: One-Fifth of Fleet Electric, September 2025. BMTC fleet covers ~61,000 trips and ~1.19 million km daily (≈19 km average per trip). https://www.sustainable-bus.com/news/bangalore-buses-one-fifth-fleet-7000/

[22] WRI India — Real-world Electric Bus Operation: Trend in Technology, Performance, Degradation, and Lifespan of Batteries, January 2024. Accelerated battery degradation in tropical environments like India's. https://wri-india.org/sites/default/files/Real-world%20Electric%20Bus%20Operation_Working%20Paper%20final%20_revised.pdf

[23] Frontiers in Future Transportation — Optimizing Electric Bus Performance via Predictive Maintenance, December 2024. High temperature, extreme state of charge, and fast charging accelerate degradation. https://www.frontiersin.org/journals/future-transportation/articles/10.3389/ffutr.2024.1506866/full